This invention relates to a materials handling device and is particularly, though not exclusively, concerned with vibratory conveyors.
Vibratory conveyors are used in many industries to move various (usually small) items from one location to another. Such conveyors usually comprise a trough mounted on a relatively massive base by means which permit the trough to be rhythmically pulsed, thereby to move items from one end of the trough to the other.
It will be appreciated that these conveyors are especially suitable for transporting food products since the trough may be of simple form and is relatively easily and economically manufactured from stainless steel or aluminum. Such troughs are also easy to clean and provide minimal obstruction to the passage of items therealong.
Vibratory conveyors are used in continuous food manufacturing processes, for example to transport frozen french fries to weighing and packing stations. Typically a series of three vibratory conveyors may be provided in line and having small gaps therebetween bridged by gates. The gates open under command to allow french fries to drop onto means for conveying the fries to one of several weighing stations. Only one weighing station is supplied at a time and the gates accordingly open and close rather frequently. Such apparatus may be in continuous use 6 days a week and for 24 hours each day, and must thus be entirely reliable since otherwise the entire preparation and packing line may come to a halt.
A typical prior art conveyor is described in detail below.
The gates of such vibratory conveyors undergo considerable stress due to the necessary vibration of the mechanism; they frequently suffer cracks and breakage. Many attempts have been made to mitigate these effects but none has been entirely successful.
The prior art gates also suffer other disadvantages in that closing of a gate may trap the product between adjacent faces of the gate and conveyor, leading to misshaped or broken product and potential jamming of the gate mechanism. Prior art gates may also require stiffeners to ensure adequate strength and rigidity, but such stiffeners obstruct the free movement of product.
A further disadvantage is that the gates rattle and thus the noise level in the immediate vicinity of the gate mechanism is extremely high mainly because the gate vibrates in its mounting and on the upstream conveyor bed. This is of considerable concern but to date no adequate method of noise reduction has been found which is reliable and effective.
Yet another disadvantage is that as the gates pivot upward (while loaded with product) they tend to throw product over the side of the conveyor; this is undesirable and dangerous and makes the mechanism especially unsuitable for a food factory.
Notwithstanding the very considerable disadvantage of vibratory conveyors with gates, these mechanisms have become the standard for use in many industries and particularly in the food industry.